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3
votes
2answers
89 views

Is there FHE (fully homomorphic encrpytion) for string/text processing?

I had a quick look at FHE libraries like SEAL, HeLib, and Palisade and they deal with addition or multiplication of encrypted data. Is there a FHE that deals with string? If no, is that because it is ...
3
votes
1answer
88 views

Is it feasible to find n hashes that sum up to a given hash?

Consider two sets $A=\{a_1,a_2,\cdots,a_n\}, B=\{b_1,b_2,\cdots,b_m\}$; We can calculate the hash sum of those sets: $$HASHSUM(𝐴)=(ℎ𝑎𝑠ℎ(a_1)+ ℎ𝑎𝑠ℎ(𝑎_2)+\cdots +ℎ𝑎𝑠ℎ(𝑎_𝑛))$$ and $$HASHSUM(𝐵...
0
votes
0answers
36 views

Constructing Differential Characteristics for Feistel Cipher

I have to construct for every i-round of Feistel cipher, for $i \in \{3,4,5,6,7,8\}$, a differential characteristic with there properties: $Pr[\Delta x = a \overset{f_i}{\rightarrow} \Delta y = b] = ...
2
votes
0answers
67 views

Is it possible to verify attributes of encrypted content?

Let's say that Alice has this information about her, { "name": "Alice", "age": 25, "eyes": "brown" } which she encrypts with a key pair so that no one access ...
1
vote
2answers
62 views

In zero knowledge proofs, would it make a difference if the prover is deterministic or probabilistic?

In zero knowledge proofs, would it make a difference if the prover is deterministic or probabilistic? As the verifier can simulate the prover's interaction with him, I assumed that the prover would ...
0
votes
1answer
40 views

Security of this PRF [closed]

Given $F$ a secure PRF with input size $\lambda$. Define $F'$ as $F'(k,x||x') = F(k, 0||x)\oplus F(k, 1||x')$ with $x$ and $x'$ of $\lambda-1$ bits. Is $F'$ a secure PRF?
1
vote
1answer
32 views

Is PKCS#5 deterministic if both sides use an agreed salt and iteration count

In a system were both sides have access to a common secret, and publicly exchange an iteration count and salt, can a PKCS#5 (Password-based Encryption Standard) algorithm be used to generate a key ...
4
votes
1answer
72 views

secp256k1 point density

I am working on a crypto project using the secp256k1 elliptic curve. I know that I can select a random point $P = (x, y)$ from the curve by randomly selecting the first coordinate $x \in \mathbb{Z}_p$...
0
votes
0answers
18 views

Generate Private Key with AES 256 CTR [migrated]

How to generate a private key with AES 256-CTR ? I need a private key with CTR as CBC is no longer supported by my client. Please advise Details: We need to connect to an SFTP instance of client ...
0
votes
0answers
31 views

MULalpha and DIValpha operations in SNOW 3G

I'm not able to appreciate the importance of mul alpha and div alpha operations in feedback polynomial of LFSR in SNOW 3G. What problems or weakness do they help in mitigating and how ?
3
votes
0answers
53 views

Lattice Based Cryptography domain

Some cryptosystems operate on the domain of the form $\mathbb{Z}_q[x]/\langle x^n-1\rangle$ and others operate on $\mathbb{Z}_q[x]/\langle x^n+1\rangle$. What's the security impact of the two forms?
2
votes
1answer
53 views

What is a randomly derived key?

It is a well-known fact that using the same key + nonce combination with a stream cipher twice breaks security. The NaCl library has different primitives for authenticated encryption (i.e., ...
0
votes
2answers
92 views

XOR and key reuse [duplicate]

I've been doing a bit of reading on the use of XOR and the dangers of key reuse. I'm aware that reusing a key can open a door for a frequency analysis attack on my plain text. So far, everything ...
0
votes
0answers
13 views

Differences between ssh-keygen private keys and libressl's? [migrated]

I generated a private key using libressl 3.0 using curve secp521r1. ...
0
votes
1answer
31 views

Question about Enigmas involutional property and its reduction of possible ciphers

I'm currently learning cryptography at a university. I can't wrap my mind around how the involutional property of Engima reduces its possible ciphers while being poly-alphabetic. Can someone please ...
0
votes
1answer
57 views

Elliptic curve with prime subgroup equal to field size

I am aware that when the equation $\#E(\mathbb{Z}_p) = p$ holds for prime $p$, the elliptic curve is called "anomalous" and is insecure do to "Smart's attack". Consider the similar case that $E(\...
0
votes
0answers
31 views

What is a nested signature in GPG and how to decrypt it in OpenPGP?

When I decrypt a file in OpenPGP (in Golang), I receive this error message: unsupported feature: nested signatures There is very little clear information about ...
0
votes
0answers
23 views

What are some best practices to handle user password in shell script and environment variables?

I'm new to this community. Currently im working on a project which involves handling user password in shell script. Following steps describe my password consumption flow: Get password from user ...
2
votes
1answer
45 views

What time is used in a TOTP counter?

I am currently working on a desktop TOTP client. From the TOTP spec at https://tools.ietf.org/html/rfc6238#section-4.1, the 6 digit OTP is generated from counter (in this case time). But what is "...
0
votes
0answers
23 views

Does it make sense to try CP-ABE in a database for a individual database records?

I'm almost ready for my graduation research project, and I'm looking for an interesting crypto-related topic. I came across CP-ABE, and since I'm working in infosec it caught my attention. Will it ...
3
votes
0answers
109 views

Are there any cryptographic methods which use multiple cyclic groups?

For some cryptographic methods you can construct them. e.g. elliptic curves (product of two cyclic groups) or Diffie–Hellman (can be product of n-cyclic groups). But they have no usage because at a ...
5
votes
2answers
386 views

Is it feasible to get a hash collision for CRC32, MD-5 and SHA-1 on one file?

I'm aware that individually, each has its weaknesses (especially CRC32), but is it feasible that a file could be created to falsely match all three?
4
votes
1answer
57 views

Why is the vector sampled from Gaussian or Subgaussian distribution in lattice-based cryptography? [duplicate]

I have known that the vector is sampled from Gaussian distribution in lattice-based cryptography because the distribution of the vector $\mod{\mathcal{P}(\mathbf{B})}$ approximates to uniform ...
0
votes
1answer
66 views

How can padding be disambiguated from data, when encrypting using a block cipher?

How can padding be disambiguated from data, when encrypting using a block cipher? I'm by no means an expert in cryptography, but rather a programmer with a keen interest. Suppose, I've ...
1
vote
1answer
39 views

What does MULx operation in SNOW 3G correspond to?

According to the spec, MULx operation is defined as - MULx maps 16 bits to 8 bits. Let V and c be 8-bit input values. Then MULx is defined: If the leftmost (i.e. the most significant) bit of V ...
0
votes
1answer
76 views

How to decide whether to use digital signature (RSA) or HMAC

I found multiple posts regarding the differences between HMAC and RSA. Why should I prefer one or the other? These are some examples: HMAC SHA256 vs RSA SHA256 - which one to use What are the ...
0
votes
0answers
27 views

Is there a constant-overhead PRP construction based on PRPs for large inputs?

Somewhat recently I learned that there's a separation between an encryption scheme being CCA2 secure and being AE secure, namely PRPs. So if we would use AES as an encryption scheme for fixed-size ...
1
vote
1answer
36 views

Calculating G for a give cyclic group mod P

For DH key agreement, one must begin with a generator of a cyclic group g. However, intuitively to me at least, it seems that g ...
2
votes
0answers
36 views

Simple explanation of CKKS scheme

I'm searching for a (preferably simple) explanation of the Cheon-Kim-Kim-Song scheme for fully homomorphic encryption. All I did find so far is the original paper, which is rather difficult to ...
3
votes
0answers
126 views

Career switch from a Statistician to Cryptography Research [closed]

I am currently working as a statistician, and I hope to do a career switch to cryptography as I have become interested in cryptography research. I currently have a bachelor's degree in mathematics as ...
1
vote
3answers
164 views

Encrypting a JPG, where the output is a scrambled JPG [duplicate]

Is there an algorithm or program that can take an image, be encrypted, still be opened by an image viewer, but is restored when decrypted? Basically I want the ability to secure images but still have ...
1
vote
2answers
51 views

How many hash collision will exist where the digest is a pre-image?

This question follows on from the question Circular hash collision where digest is pre-image: Could hash(a) = b, hash(b)=c, then hash(c)=a? The question was answered but the issue of the number of ...
0
votes
0answers
46 views

What is the proper approach to software licensing system? [duplicate]

I am willing to create a server side licensing system for my commercial softwares but not really sure what cryptography method I should be using for best possible security per the standard of modern ...
1
vote
0answers
36 views

Sigma Protocol with Privacy-preserving Discrete Logarithms?

I've been reading up on Sigma Protocols and Fiat-Shamir Heuristic. There is a small problem I see here that is possibly already solved, but I'd like to know if it has a solution. Peggy wants to prove ...
-3
votes
1answer
51 views

Is this a Matrix for AES, and why? [on hold]

My task is to check if this S-BOX is an AES S-BOX. My Idear is, that you cant use it because 16 - 10 and 17 - 9 will give you the same output. Given Matrix:
1
vote
1answer
54 views

Decrypt authenticated cipher while still encrypting [duplicate]

Normal AES-GCM generates an authentication tag at the end of encryption. I want to decrypt it while it is still being encrypted. This would be useful to send, encrypt, receive and decrypt a large file ...
44
votes
4answers
9k views

Why isn’t SHA-3 in wider use?

SHA-3 was released by NIST just over 4 years ago this week. In my experience it does not seem to be as widely used as I might have expected. I see SHA-2 and even SHA-1 more often. What are your ...
1
vote
2answers
67 views

Using public-key signature instead of having API key

I am designing an application that will need an API key. At first I believed that generating a long, random token would be secure enough (say 32 chars string that includes 0-9, a-z and A-Z), and then ...
-1
votes
0answers
24 views

Is there some libraries or implement of GSW13 homomorphic encryption? [migrated]

I am doing research related to homomorphic encryption and need to implement the third generation homomorphic encryption proposed in GSW13Homomorphic Encryption from Learning with Errors: Conceptually-...
3
votes
0answers
44 views

Do people sign my subkey?

So, I've generated my GPG key pair. Created a subkey for signing and a subkey for encryption. Exported the whole thing, removed my master key pair to a secure place, re-imported only the subkeys. Now, ...
2
votes
1answer
51 views

How is Encryption Actually Used in Public Networks at This Moment?

Has anyone done a study, assembled a snapshot, of how encryption is actually being used on the Internet at this moment? So many companies do traffic analysis, the usage share of operating systems, ...
3
votes
1answer
127 views

Circular hash collision where digest is pre-image: Could hash(a) = b, hash(b)=c, then hash(c)=a?

For any SHA-family of algorithms (including Keccak) except for SHA1, would it be theoretically possible for there to exist a pre-image a whose hash digest ...
1
vote
1answer
67 views

Risks of publishing multiple signatures

Is there a risk when publishing multiple signatures for the same message? For instance, an ECDSA key (using an EC key) and a RSA-PSS signature (using a RSA key). The context of my question is the use ...
4
votes
1answer
103 views

How exactly is TFHE secure?

TFHE (Fully Homomorphic Encryption over Torus) seems to be a state-of-the-art form of homomorphic encryption. But, I got a bit confused. I have recently read the paper Fully Homomorphic Encryption ...
2
votes
1answer
41 views

TLS_DH_RSA_* cipher, how can static DH use an RSA certificate?

I am confused about TLS_DH_RSA_* ciphers because, for DH to work, the server certificate has to include a DH public key, but for server authentication the server certificate needs an RSA public key. ...
1
vote
0answers
53 views

Are two keys derived from the same password vulnerable to a related key attack?

Background I am currently writing a password manager application. As usual, the passwords are put in a file encrypted using a user-entered password. I'm using the NaCl library but actually it's not ...
1
vote
2answers
75 views

Confusing terminology about stream ciphers

In their book, Understanding Cryptography, on page 37, Christof Paar and Jan Pelzel write: Definition 2.2.2 One-Time Pad (OTP) A stream cipher for which the key stream s0,s1,s2,... is ...
-1
votes
1answer
62 views

Can't understand the magic of relationship between private an public key functions

To encrypt a message $$ P = 53, Q=59, n=PQ=3127, e =3 $$ let message M, for example, $ 89 $$ cipher = 89^{e}mod\quad n. $$ cipher = 1394 this is the encrypted message $$ \phi=(P-1)(Q-1)=3016 $$ $$...
1
vote
1answer
26 views

Signing a binary hash vs character representation of the same hash

I have a hash that I want to sign, with the hexadecimal representation: hash_bin=0x11223344 (length 4 bytes). The same hash also has a character representation hash_text=”11223344”, which is the ...
0
votes
0answers
106 views

How can I encrypt a password for storage without having to remember another password? [migrated]

I've recently started using a password manager (1Password). I have a really good master password (using diceware) but I'm worried that if I forget it then I can't access 1P and all my passwords. One ...

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